In an exposure apparatus used in the lithography process for producing semiconductor devices, etc., the wavelength of exposure light (exposure light beam) is progressively shortened so as to enhance the resolution. In the recent years, an exposure apparatus which uses, as the exposure light, a laser beam of which wavelength is in the range of the deep ultraviolet region to the vacuum ultraviolet region, such as ArF or KrF excimer laser. Further, there is also developed an exposure apparatus (EUV exposure apparatus) using, as the exposure light, an Extreme Ultraviolet Light (hereinafter referred to as “EUV light”) including soft X-ray of which wavelength is about not more than 100 nm. In these exposure apparatuses, the wavefront aberration of projection optical system needs to be measured with high accuracy.
As a conventional measuring device for measuring the wavefront aberration, there is known a measuring device based on the shearing interference system in which a plurality of pinholes, etc. are arranged in rows in a predetermined manner on an object plane of an projection optical system; light beams generated from the pinholes are allowed to pass (be transmitted) via the projection optical system and a diffraction grating having a pattern composed of a large number of rectangular-shaped openings periodically arranged in two mutually orthogonal directions; and an interference fringe, produced by interference between laterally-shifted or deviated wavefronts of a plurality of diffracted lights generated (exiting, outgoing) from the diffraction grating, is optically received by an imaging element (see, for example, Japanese Patent Application Laid-open No. 2007-173461).